EKSONIC AERAS REVIEW
Thanks to the kind generosity of
@Kerry , the proprietor of Eksonic, I was able to home demo the Eksonic Aeras estat amp for the past month. I was able to listen fairly extensively to the Aeras in comparison to my NAD/iESL setup, with both my recently purchased STAX SR-X9000, as well as with the STAX SR-009S, which I had purchased a couple of months ago as a stopgap until my X9K arrived.
To facilitate easy comparisons between the Aeras and the iESL, I simultaneously used both the RCA and XLR outputs from my reference DAC, the EMM Labs DA2 V2. I also inserted my Benchmark DAC3 into the chain
before the Aeras to convert RCA (DAC output) to XLR (Aeras input), as well as to provide remote control of volume and muting. The DAC3 is a middling DAC in my opinion, but its preamp section is quite superb and very transparent based on critical A/B testing I've done in the past. That said, the Aeras arguably would have sounded even better with a direct XLR connection from my EMM Labs DAC. For completeness, here are the respective chains used in my listening sessions:
DA2 V2 DAC (XLR) ---> Audio Research Ref 6SE Preamp (XLR) ---> NAD M22 V2 ---> iFi iESL Energizer ---> Estat headphone
DA2 V2 DAC (RCA) ---> Benchmark DAC3 (RCA analog in, XLR out) ---> Eksonic Aeras ---> Estat headphone
=========
Before discussing sonic impressions, herewith a brief digression on the
ergonomics of the Aeras amplifier. The Aeras represents trickle-down technology from the universally highly acclaimed Eksonic DIY T2 estat amp, in a
much smaller form factor and at roughly half the cost. The Aeras features a single (rear) XLR input and a single STAX Pro-Bias headphone jack. There is also a large volume knob and a power switch with a ring LED on the front panel. The volume is not controllable remotely. After being switched ON, the Aeras enters standby (muted) mode, indicated by the power LED flashing, as well as a handful of red LEDs illuminating near the front of the complement of four (4) 6S4A tubes socketed atop the amp. After perhaps 30-45 seconds (I never timed it), the Aeras comes out of standby (and unmutes), indicated by the power LED transitioning from flashing to solid ON, as well as another dozen or so red LEDs illuminating throughout the region of the tube sockets. Operation was extremely straightforward, and I encountered no glitches whatsoever during my month of use.
Aesthetics are subjective, but I find the Aeras to be
a very attractive piece of gear. There is an elegance, not to mention tremendous practicality, in its compact form factor. Fit and finish are exceptional. There are no sharp edges on the heat sinks or elsewhere, and the matte finish to the metalwork is beautiful. The Aeras would be a top choice for an estat amp to fit on a desk or bedside table, or to take on the road.
I should note that the Aeras operates in class A and gets very warm. Several seasoned estat folks have pointed out that this is true of virtually all the well-known estat amps, whether tube or solid state. The Aeras may be slightly disadvantaged in dissipating heat due to its smaller form factor. Even though we live near the coast and don't have A/C in our house, the heat from the Aeras didn't noticeably affect ambient room temperature. My only minor niggle was that the front panel and volume knob also got rather warm to the touch after a period of continuous operation. I did mention this to Kerry, and he told me it may be possible to improve thermal isolation of the volume knob, but probably not the front panel. Since I was controlling volume remotely, I really only noticed this when plugging/unplugging a headphone, and it wouldn't be a deal-breaker for me in any case.
Sonic Impressions
The Aeras arrived prior to the STAX SR-X9000, so my initial evaluation was done using the STAX SR-009S (and briefly, the Hifiman Shangri-la Junior). I'd had the 009S for maybe a week prior to the arrival of the Aeras, so I'd formed an initial impression of the headphone driven from my iESL. Generally, I really liked what I was hearing from that combo. Bass was definitely elevated compared to my Shang Junior, and the timbre was more realistic than I'd remembered it from other auditions, typically on the BHSE. The technical proficiency of the 009S is high, if not quite state-of-the-art, and it exhibits most of the virtues of the better estats, while committing no overt sins of any real consequence. I found the tuning of the 009S through the NAD/iESL combo to work well for virtually all genres of music.
So what were the differences when moving the 009S over to the Aeras? In a nutshell, the Aeras served up an increase in treble energy. The subjective results of that were better depth and layering of the soundstage (with maybe a
slight decrease in width), more shimmer and air around cymbals, and an increased vibrancy/glow to the music overall. I hadn't felt like something was missing with the iESL chain, but once I moved to the Aeras, music just sounded more energized and lifelike. The only downside of the Aeras/009S pairing was that the
occasional recording exhibited a bit of heat or glare in the treble. I'd sometimes noticed this before with the BHSE/009S pairing, and
I'd mostly attribute it to the 009S, as it was never an issue with the Aeras later driving the X9K. It's also highly likely the issue could be addressed via EQ, but I didn't bother to experiment with it since I knew the X9K was on the way at that point.
After the X9K arrived, I really didn't listen to the 009S anymore. As expected, the X9K also exhibited a bit more treble energy when driven by the Aeras vs. the NAD/iESL. Subjectively, however, the differences between the amps weren't as prominent when listening to the X9K. There was still an increase in soundstage depth/layering with the Aeras, and a bit more shimmer/air around cymbals, but the baseline established by the NAD/iESL/X9K combo was so excellent that the improvements from the Aeras seemed more incremental than they had with the 009S.
I still think a majority of listeners would prefer the Aeras (as do I, in general), especially those who find the X9K a tad reticent in the treble region. There were occasions where I felt the iESL chain had a bit tighter grip on the bass than did the Aeras, but it was close enough that I couldn't say for sure. I will also note that when I listened to either amp for a period without switching, my ears seemed to adapt, and I was able to just normalize and enjoy whatever I was hearing at the moment. One takeaway from this experience was that the NAD/iESL is not a second rate option for driving estats by any measure. It may not be at the top of the mountain, but it's within shouting distance. Of course, I've only heard the Eksonic DIY T2 briefly at CanJam, and not with the X9K, so the gap may in fact be much wider than I'm imagining.
Bottom line: I would recommend the Eksonic Aeras without reservation! Paired with the STAX SR-X9000, the sound quality was nothing short of spectacular. The Aeras also sounded fantastic with the STAX SR-009S. The only headphone which I preferred driven by the iESL was the Hifiman Shangri-la Junior. It's a rather bright estat to begin with, and it had better synergy with the iESL chain to my ears.
As always, one listener's subjective opinion. YMMV.